Electron multiplier having dynode modules

ABSTRACT

An electron multiplier construction formed of a plurality of dynode modules. Each module is formed of a a ceramic wafer having two complementary, metal dynode elements attached thereto arranged to direct a stream of electrons through an opening in the wafer and into a dynode element of the next successive module. The modules are secured together in spaced, parallel relationship by metal post elements spaced-apart around the periphery of the wafers, each dynode element being connected to a different one of the post elements.

[151 3,684,910 [451 Aug. 15, 1972 United States Patent Stutzman et al.

2,464,076 3/1949 De Gier...................313/70 X 2,757,307 7/1956 Sixet al. ................313/257 X 3,229,143 H1966Bartschat...................313/105 Primary Exanu'nerRobert Sega]Att0rney--C. Cornell Remson, J12, Walter J. Baum Percy P. Lantzy, PhilipM. Bolton, Isidore To a gut,

Charles L. Johnson, Jr. and Hood, Gust, Irish & Lundy graph Corporation,Nutley, NJ.

221 Filed: May 18,1970

211 Appl.No.: 38,092

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ATTORNEYS PAIENTEDws 15 m2 SHLEI 3 OF 4 INVENTORS GUY R. STUTZMAN ALLANJ. COMSTOCK X/MO,M,M

ATTORNEYS PATENTEDAUB 15 m2 SHEET b [1F 4 lE lE INVENTORS BACKGROUND OFTHE INVENTION '1. Field of the Invention This invention relatesgenerally to electron multiplier constructions, and more particularly toa modular assembly of dynode elements for an electron multiplier.

2. Description of the Prior Art Conventional electron multiplierscomprise a plurality of discrete stages or dynodes operated atprogressively increasing potentials. The dynodes are formed of or coatedwith secondary emissive material and are arranged so that electronsinjected into the low potential end of the device are multiplied upondynode impact, thus resulting in the generation of secondary electronswhich are accelerated to a succeeding dynode stage where the processrecurs, hence giving rise to an overall cascade multiplication ofelectrons. An electron multiplier is commonly enclosed in an evacuatedenvelope and the progressively increasing potentials are normallyobtained from an external resistance divider network and applied to thedynodes through a multilead stem. In conventional electron multiplierconstructions, each of the dynodes is independently mounted andelectrically isolated from adjacent dynodes thus providing aconstruction which is complex, difficult to assemble, and thus costly.Further, the use of such floating or free-standing dynodes results in afragile construction which is not well suited to applications subject toshock.

SUMMARY OF THE INVENTION In order to provide a rugged electronmultiplier construction, particularly suitable for use in airborneapplications, the multiplier comprises a plurality of dynode age dividernetwork are printed or otherwise deposited on the supporting members.

In its broader aspects, the invention provides a dynode assembly havinga support plate member formed of insulating material with an openingtherethrough. A pair of complementary dynode elements formed ofrelatively thin sheet material are respectively attached to the supportmember, the dynode elements being exposed to the opening and arranged sothat a stream of electrons is directed from one dynode element to theother through the opening.

It is an object of the present invention to provide an improved electronmultiplier construction.

Another object of the invention is to provide a rugged electronmultiplier construction.

A further object of the invention is to provide an electron multiplierconstruction formed of a plurality of dynode modules.

A still further object of the invention is to provide a modular electronmultiplier construction wherein each module includes resistance elementswhich collectively comprise a self-contained, voltage dividingresistance network.

2 BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and otherfeatures and objects of this invention and the manner of attaining themwill become more apparent and the invention itself will be bestunderstood by reference to the following description of the embodimentsof the invention taken in con junction with the accompanying drawings,wherein:

FIG. 1 is an exploded view in perspective illustrating one embodiment ofthe electron multiplier construction of the invention;

FIG. 2 is a cross-sectional view, taken generally along the line 2--2 ofFIG. 1, and further illustrating the electron multiplier construction ofthe invention assembled within an enclosed envelope;

FIG. 3 is a fragmentary view, partly in cross-section, illustrating themethod of attaching the stem leads to the module supporting posts;

FIG. 4 is a view in perspective illustrating one form of dynode elementusable in the invention;

FIG. 5 is a side view further showing the electron multiplier of theinvention using the dynode elements of FIG. 4;

FIG. 6 is a perspective of another form of dynode element usable in theinvention;

FIG. 7 is a side view showing a modular construction employing thedynode elements of FIG. 6;

FIG. 8 is a top view showing a wafer element employed in anotherembodiment of the invention;

FIG. 9 is a top view of one dynode module assembled with the waferelement of FIG. 8 and having voltage dividing resistance elementsprinted on the wafer element;

FIG. 10 is a fragmentary cross-sectional view taken generally along theline 10-10 of FIG. 9;

FIG. 1 1 is a schematic illustration showing a modular electronmultiplier assembly and voltage divider network incorporating themodules of FIG. 9; and

FIG. 12 shows the arrangement of the individual modules and voltagedividing resistors to provide the assembly of FIG. 1 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2of the drawings, the improved modular electron multiplier assembly ofthe invention, generally indicated at 10, is shownas comprising fivedynode modules 11, 1.2, 13, 14, and 15. Each of the modules comprises acircular supporting plate or wafer 16, preferably formed of ceramicmaterial, and having a rectangular opening 17 therethrough adjacent thecenter. A pair of complementary, bucketshaped dynode elements formed ofrelatively thin sheet metal having secondary emissive properties, orbeing coated with secondary-emissive material, is positioned in theopening 17 of each of the ceramic wafers 16, the dynode elements beingdisposed to receive an input stream of electrons, to direct andaccelerate the stream from one of the dynodes to the other through therespective opening 17, and finally to direct and accelerate the streamto the input dynode of the next successive module.

More particularly, a pair of identical, complementary dynode elements 18and 19 are provided seated in opening 17 of ceramic wafer 16 of module11, dynode 18 being the input, low potential dynode for receiving aninput stream of electrons, as indicated by the dashed line 20 in FIG. 2.In response to the application of suitable potentials to dynode elements18 and 19, the stream of electrons is directed and accelerated fromdynode element 18 to dynode element 19, and thence to dynode element 22of the next successive module 12, as shown by the dashed lines 23 inFIG. 2, and as well known to those skilled in the art.

Dynode elements 18 and 19 are respectively provided with opposed,outwardly extending ears 24, 25, and 26, 27 which engage the upper side28 of ceramic wafer 16, being rigidly attached thereto, such as by spotwelding to a pad metalized on wafer 16, as indicated in dashed lines at31.

Similarly, module 12 comprises ceramic wafer 29 and dynode elements 30and 32, module 13 comprises ceramic wafer 33 and dynode elements 34 and35, module 14 comprises ceramic wafer 36 and dynode elements 37 and 38,and module comprises ceramic wafer 39 and dynode elements 40 and 42, allof the dynode elements being similarly positioned in the respectiveopening 17 and similarly rigidly attached to the upper side of therespective ceramic wafer by ears 24, 25, 26 and 27. Inspection of FIG. 2will reveal that the dynode elements 18 and 19, 30 and 32, 34 and 35, 37and 38, and 40 and 42 are disposed in conventional arrangement so thatas to accelerate and multiply the stream of electrons successively fromthe input dynode element 18 to final or output dynode element 42.

The ceramic wafers 16, 29, 33, 36, and 39 are maintained in spaced,parallel relationship by a plurality of 5 post members 43 equally spacedaround the ceramic wafers respectively adjacent the peripheral edges,there being ten such post elements 43 between each adjacent pair ofceramic wafers in the illustrated embodiment in which there are tendynode elements. Each of the post members 43 comprises a hollow metaltube 44 having its upper end 45 snugly seated in an opening 46 in therespective ceramic wafer and rigidly secured thereto, as by brazing, theinterior wall of opening 46 having previously been metalized. Thetubular spacing members 44 extend toward the adjacent ceramic wafer in adirection normal to the wafer, and have their other ends 47 abutting theupper end 46 of the adjacent tubular element. As shown in FIGS. 1 and 2,corresponding tubular spacing elements 43 are in axial alignmentrespectively to receive pins or stem lead wires 48.

The modules 11, 12, 13, 14 and 15 are rigidly held in assembled relationby welding the stem lead wires 48 to the respective tubular spacingmembers 44. Referring particularly to FIGS. 2 and 3, each of the tubularspacing elements 44 preferably has a cut-out portion 49 formed thereinexposing side wall portion 50 of the respective stem lead wire 48.Welding electrodes 52, 53 are then respectively engaged with exposedportions 50 of the stem lead wire 48 and the tubular spacing elements44, as shown in FIG. 3, application of a suitable potential thusspot-welding the stem lead wire 48 to the respective lower and uppertubular end spacing element 44-1 and 44-2 so as to hold the modules inassembled relation. The use of equal length tubular elements 44 permitsprecision spacing of the wafers.

It will now be observed that the circular array of 10 post elements 43comprising the tubular space members 44 and stem lead wires 48 provide aconvenient means for making electrical connections to the respectivedynode elements. Thus, thick film electrical leads 54, 55 respectivelyconnect cars 24 and 27 of dynode elements 18 and 19 to the upper ends ofpost members 43-1 and 43-2. The thick film conductors 54 and 55 arerigidly attached to the upper surface 28 of ceramic wafer 11, preferablybeing printed thereon by any conventional method. Similarly, thick filmleads 56 and 57 respectively connect dynodes 30 and 32 to the postmembers 43-3 and 434 leads 58 and 59 respectively connect dynodeelements 34 and 35 to post members 43-5 and 43-6, leads 60 and 62respectively connect dynode elements 37 and 38 to post members 43-7 and43-8, and leads 63 and 64 respectively connect dynode elements 40 and 42to post members 43-9 and 43-10.

Particular reference to FIG. 3 will reveal that the lower end 47 of arespective tubular member 44 abuts the termination portion 65 of arespective lead which surrounds the respective stem lead wire 48,thereby insuring a good electrical connection to the respective stemlead wire.

Referring particularly to FIG. 2, the dynode module assembly 10 may bepositioned within the cylindrical portion 66 of an enclosing envelope ofa tube incorporating an electron multiplier, such as a photo-multipliertube or image dissector tube, cylindrical portion 66 having an end wall67 through which the projecting portions 68 of the stem lead wires 48,extend, being sealed thereto as at 69. A suitable target or collectorelectrode 70 may be positioned to receive the multiplied electron stream72 from the final dynode element 42. In the case of an image dissectortube, an element 72 is provided extending across the tube and havingaperture 73 through which the input electron stream 20 is passed to theinitial dynode element 18, as is well-known to those skilled in the art.

Referring now to FIG. 4, the dynode elements employed in the embodimentillustrated in FIGS. 1 and 2 may comprise a bucket-shaped portion 74 ofrelatively thin metal which may be conventionally formed by etching froma blank and then by stamping to the desired configuration. A generallyU-shaped member 75, likewise formed of relatively thin metal, embracesthe lower part of portion 74, being secured thereto in any suitablemanner, as by spot welding, and has mounting ears 24, 27, and 25, 26integrally formed thereon and extending outwardly therefrom, as shown.

Referring now to FIG. 5 in which the dynode elements of the type shownin FIG. 4 are shown assembled in the multiplier assembly 10 of FIGS. 1and 2, it will be seen that the cars 24, 25, 26, 27 of each dynodeelement are arranged in abutting relationship with the upper surface 28of each wafer 16, 29, 33, etc.

Referring now to FIG. 6, another form of dynode element 76 may beemployed comprising a unitary bucket-shaped member 77 formed ofrelatively thin sheet metal and having integral supporting ears 78, 79formed thereon and extending outwardly thereon, as shown.

Referring briefly to FIG. 7 in which there is shown an assemblyutilizing the dynode elements 76 of the type shown in FIG. 6, it will beseen that the dynode elements are disposed in cooperative relationship,as shown, with their mounting ears 78, 79 respectively engaging both theupper and lower sides of the respective ceramic wafers, as shown.

Referring now to FIGS. 8-12 in which like elements are indicated by likereference numerals and similar elements by primed reference numerals,there is shown an embodiment of the invention in which a pair of voltagedividing resistors is printed on each wafer along with circuitconnections so that, when the multiplier is assembled, the resistors onall of the wafers are coupled in a voltage dividing network. Here,ceramic wafer 16' is provided having peripheral holes 46' opening 17,and holes 80 formed therein, such as by punching before firing theceramic, or by ultrasonic abrasive machining after firing. Wafers 16'may be formed of suitable ceramic material, such as a high alumina whichis fired at an elevated temperature.

The interior walls of holes 46, 80 and a small area surrounding theholes on the upper surface 28 of wafer 16' are metalized, as at 82, 84(FIG. 10). Metalizing of the holes may be accomplished with aconventional screen process employing a suitable metalizing material,such as molybdenum manganese. Plugs 86 are formed of a suitable lowexpansion alloy, such as Kovar, are then inserted in the metalized holes80 and brazed thereto, plugs 86 thus providing a rugged mounting for thedynode ears or tabs which are subsequently brazed thereto. The uppersurface 28 of wafer 16' is then preferably polished in a lappingoperation to render it suitable for use as a substrate for the circuitryto be printed thereon.

Dynode elements 18, 19 are then positioned in opening 17 and their ears24', 25, 26', 27' spot welded to plugs 86, as at 88. Thick filmresistors R1, R2 and electrical leads 90, 92, 94 are then formed onupper surface 28 on wafer 16, as by means of screen printing or vacuumdeposition. Tubular spacing elements 44 are then inserted in themetalized openings 46' and brazed thereto. In the illustratedembodiment, a total of 12 openings 46' and tubular spacing elements 44are provided. It will be observed that in the case of a particular wafer16' which forms the first dynode module 11' (FIGS. 11 and 12), lead 90couples post member 43-1 to one end of resistor R2, lead 92 couples theother end of resistor R2 and one end of resistor R1 to ear 25' of dynodel8, and lead 94 couples the other end of resistor R1 to ear 26' ofdynode 19 and to post element 43-3.

Referring now additionally to FIGS. 11 and 12, a suitable cathode 96 mayalso be coupled to post 43-1 by lead 98, and post 43-1 may be coupled toexternal terminal 100. In the second dynode stage 12, lead 102 couplespost element 43-3 to resistor R3, lead 104 couples resistors R3 and R4to dynode 30, and lead 106 couples resistor R4 and dynode 32 to postelement 43-5. In module 13', lead 108 couples post element 43-5 toresistor R5, lead 110 couples resistors R5 and R6 to dynode 34, and lead112 couples resistor R6 and dynode 35 to post element 43-7. In module14' lead 1 14 couples post element 43-7 to resistor R7, lead 116 couplesresistors R7 and R8 to dynode 37, and lead 118 couples resistor R8 anddynode 38 to post element 43-9. In the final dynode module lead 120couples post element 43-9 to resistor R9, lead 122 couples resistors R9,R10 to dynode 40, and lead 124 couples resistor R10, dynode 42 andtarget or collector electrode to post element 43-11. Post element 413-has another external temiinal 126 coupled thereto.

It will now be seen that with the arrangement and connection of theresistors R1-R10 as above-described to the various dynodes and postelements 43, resistors R1-R10 are coupled in a voltage dividing networkacross external terminals 100, 126. It will be observed that only twoexternal connections are required and thus, that it is only necessary tobring the rod elements 48 of two of the post elements, i.e. 43-1 and43-11 out through the envelope end wall 67. It will be seen further thatonly six of the post elements, i.e. 43-1, 43-3, 43-5, 43-7, 43-9 and43-11 are employed for making connections to the voltage dividingresistors Rl-Rl0 and the dynodes, the remaining intermediate postelements being desirably employed only for providing a rugged assemblyof the dynode modules.

It will be observed that the modular construction incorporating thewafers 16, 29, et seq, and the post elements 43 can be employed tosupport the elements of tubes other than electron multipliers, and thatall of the circuitry for the tubes, not merely voltage dividers, may beimprinted on the wafers.

It will be seen that each module is seperately assembled and forms acomplete unit which can be tested, such as for output, prior to theassembly of the entire device. It will further be seen that the spacingbetween modules is precisely controlled by the post elements 43, andthat the spacing between the modules may be varied, as desired, bymerely varying the lengths of the post elements 43. Finally, it will beseen that the modular construction of the invention lends itself tominiaturization and in a specific embodiment, the wafers areapproximately 0.9 inch in diameter. It will now be seen that theinvention provides a modular electron multiplier assembly which ischaracterized by its ruggedness and ease of assembly from a relativelyfew number of readily fabricated component parts.

While there have been described above the principles of this inventionin connection with specific apparatus, it is to be clearly understoodthat this description is made only by way of example and not as alimitation to the scope of the invention.

What is claimed is:

1. An electron multiplier comprising:

a plurality of pairs of successive longitudinally disposed electronmultiplier dynodes,

a plurality of successive longitudinally disposed spaced parallelinsulating support discs having centrally disposed openings, each discsupporting a complementary pair of said dynodes in said opening arrangedto direct electrons from one dynode of said pair to the other, each saiddisc including a plurality of like apertures spaced around the peripherythereof and a plurality of hollow metal connecting posts mounted on eachsaid disc and having an end extending from said apertures on one side ofeach said disc, said apertures and posts of each disc being aligned withsaid apertures and posts of each other disc, each said end extending thedistance between discs to abut the opposite side of the next adjacentsupport disc, each pair of dynodes on each respective disc beingconnected between a selective pair of said posts different from eachother disc, and

a plurality of lead wires passing through the respec:

tive aligned apertures and posts and connecting said plurality ofaligned posts of successive discs together in a predetermined patternfor establishing progressively increasing potentials on successivedynodes, including two voltage dividing re sistors printed on saidsupport disc and connected between each said dynode and a respectivepost on each said disc wherein one end of each of said resistors isconnected to a respective post, the other ends of both of said resistorsbeing connected to one of said dynodes, the other of said dynodes beingconnected to one of said posts, said successive pairs of dynodes beingarranged in alignment for directing a stream of electrons from each pairthrough successive said pairs.

2. The assembly of claim 1, wherein one dynode of each respective saidcomplementary pair faces one side of each respective disc and the otherdynode of each said pair faces the other side of said disc.

3. The assembly of claim 2 wherein said support discs are formed ofceramic material.

4. The assembly of claim 3 wherein each of said posts comprise a metaltube attached to said support disc, and a pin element extending intosaid tube and attached thereto.

5. The assembly of claim 3 wherein each of said dynodes has a pair ofears extending therefrom, the ears of each of said dynodes beingattached to a side of said support disc thereby attaching the respectivedynode thereto.

6. The assembly of claim 5 wherein said apertures have metal plugmembers seated therein and secured thereto, said ears being respectivelysecured to said plug members.

7. The assembly of claim 6 wherein the walls of said apertures aremetalized, said plug member being brazed to said metalized walls, saidears being welded to said plug members.

8. The assembly of claim 1 further comprising an enclosing envelopehaving a generally cylindrical portion closed by an end wall, saidsupport discs being positioned in said cylindrical portion with theirperipheral edges closely adjacent the inner wall thereof.

1. An electron multiplier comprising: a plurality of pairs of successivelongitudinally disposed electron multiplier dynodes, a plurality ofsuccessive longitudinally disposed spaced parallel insulating supportdiscs having centrally disposed openings, each disc supporting acomplementary pair of said dynodes in said opening arranged to directelectrons from one dynode of said pair to the other, each said discincluding a plurality of like apertures spaced around the peripherythereof and a plurality of hollow metal connecting posts mounted on eachsaid disc and having an end extending from said apertures on one side ofeach said disc, said apertures and posts of each disc being aligned withsaid apertures and posts of each other disc, each said end extending thedistance between discs to abut the opposite side of the next adjacentsupport disc, each pair of dynodes on each respective disc beingconnected between a selective pair of said posts different from eachother disc, and a plurality of lead wires passing through the respectivealigned apertures and posts and connecting said plurality of alignedposts of successive discs together in a predetermined pattern forestablishing progressively increasing potentials on successive dynodes,including two voltage dividing resistors printed on said support discand connected between each said dynode and a respective post on eachsaid disc wherein one end of each of said resistors is connected to arespective post, the other ends of both of said resistors beingconnected to one of said dynodes, the other of said dynodes beingconnected to one of said posts, said successive pairs of dynodes beingarranged in alignment for directing a stream of electrons from each pairthrough successive said pairs.
 2. The assembly of claim 1, wherein onedynode of each respective said complementary pair faces one side of eachrespective disc and the other dynode of each said pair faces the otherside of said disc.
 3. The assembly of claim 2 wherein said support discsare formed of ceramic material.
 4. The assembly of claim 3 wherein eachof said posts comprise a metal tube attached to said support disc, and apin element extending into said tube and attached thereto.
 5. Theassembly of claim 3 wherein each of said dynodes has a pair of earsextending therefrom, the ears of each of said dynodes being attached toa side of said support disc thereby attaching the respective dynodethereto.
 6. The assembly of claim 5 wherein said apertures have metalplug members seated therein and secured thereto, said ears beingrespectively secured to said plug members.
 7. The assembly of claim 6wherein the walls of said apertures are metalized, said plug memberbeing brazed to said metalized walls, said ears being welded to saidplug members.
 8. The assembly of claim 1 further comprising an enclosingenvelope having a generally cylindrical portion closed by an end wall,said support discs being positioned in said cylindrical portion withtheir peripheral edges closely adjacent the inner wall thereof.